Use an atomic unique_ptr for the device's context array

4 files changed, 13 insertions, 37 deletions

diff --git a/alc/alc.cpp b/alc/alc.cpp
index af68e4d0..cc25177d 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -2719,8 +2719,7 @@ ALC_API ALCcontext* ALC_APIENTRY alcCreateContext(ALCdevice *device, const ALCin
          * old array.
          */
         auto *oldarray = device->mContexts.load();
-        const size_t newcount{oldarray->size()+1};
-        std::unique_ptr<ContextArray> newarray{ContextArray::Create(newcount)};
+        auto newarray = ContextArray::Create(oldarray->size() + 1);
 
         /* Copy the current/old context handles to the new array, appending the
          * new context.
@@ -2731,12 +2730,8 @@ ALC_API ALCcontext* ALC_APIENTRY alcCreateContext(ALCdevice *device, const ALCin
         /* Store the new context array in the device. Wait for any current mix
          * to finish before deleting the old array.
          */
-        dev->mContexts.store(newarray.release());
-        if(oldarray != &DeviceBase::sEmptyContextArray)
-        {
-            std::ignore = dev->waitForMix();
-            newarray.reset(oldarray);
-        }
+        auto prevarray = dev->mContexts.exchange(std::move(newarray));
+        std::ignore = dev->waitForMix();
     }
     statelock.unlock();
 
@@ -2817,7 +2812,7 @@ ALC_API ALCboolean ALC_APIENTRY alcMakeContextCurrent(ALCcontext *context) noexc
          * the current context as its refcount is decremented.
          */
     }
-    ContextRef{ALCcontext::sGlobalContext.exchange(ctx.release())};
+    ctx = ContextRef{ALCcontext::sGlobalContext.exchange(ctx.release())};
     ALCcontext::sGlobalContextLock.store(false, std::memory_order_release);
 
     /* Take ownership of the thread-local context reference (if any), clearing
diff --git a/alc/context.cpp b/alc/context.cpp
index 0f6dbbae..67f08aee 100644
--- a/alc/context.cpp
+++ b/alc/context.cpp
@@ -263,12 +263,8 @@ void ALCcontext::deinit()
     if(auto toremove = static_cast<size_t>(std::count(oldarray->begin(), oldarray->end(), this)))
     {
         using ContextArray = al::FlexArray<ContextBase*>;
-        auto alloc_ctx_array = [](const size_t count) -> ContextArray*
-        {
-            if(count == 0) return &DeviceBase::sEmptyContextArray;
-            return ContextArray::Create(count).release();
-        };
-        auto *newarray = alloc_ctx_array(oldarray->size() - toremove);
+        const size_t newsize{oldarray->size() - toremove};
+        auto newarray = ContextArray::Create(newsize);
 
         /* Copy the current/old context handles to the new array, excluding the
          * given context.
@@ -279,14 +275,10 @@ void ALCcontext::deinit()
         /* Store the new context array in the device. Wait for any current mix
          * to finish before deleting the old array.
          */
-        mDevice->mContexts.store(newarray);
-        if(oldarray != &DeviceBase::sEmptyContextArray)
-        {
-            std::ignore = mDevice->waitForMix();
-            delete oldarray;
-        }
+        auto prevarray = mDevice->mContexts.exchange(std::move(newarray));
+        std::ignore = mDevice->waitForMix();
 
-        stopPlayback = newarray->empty();
+        stopPlayback = (newsize == 0);
     }
     else
         stopPlayback = oldarray->empty();
diff --git a/core/device.cpp b/core/device.cpp
index a5edf63c..795a9601 100644
--- a/core/device.cpp
+++ b/core/device.cpp
@@ -12,15 +12,9 @@
 static_assert(std::atomic<std::chrono::nanoseconds>::is_always_lock_free);
 
 
-al::FlexArray<ContextBase*> DeviceBase::sEmptyContextArray{0u};
-
-
-DeviceBase::DeviceBase(DeviceType type) : Type{type}, mContexts{&sEmptyContextArray}
+DeviceBase::DeviceBase(DeviceType type)
+    : Type{type}, mContexts{al::FlexArray<ContextBase*>::Create(0)}
 {
 }
 
-DeviceBase::~DeviceBase()
-{
-    auto *oldarray = mContexts.exchange(nullptr, std::memory_order_relaxed);
-    if(oldarray != &sEmptyContextArray) delete oldarray;
-}
+DeviceBase::~DeviceBase() = default;
diff --git a/core/device.h b/core/device.h
index 9ee07454..1da08727 100644
--- a/core/device.h
+++ b/core/device.h
@@ -181,11 +181,6 @@ enum class DeviceState : uint8_t {
 };
 
 struct DeviceBase {
-    /* To avoid extraneous allocations, a 0-sized FlexArray<ContextBase*> is
-     * defined globally as a sharable object.
-     */
-    static al::FlexArray<ContextBase*> sEmptyContextArray;
-
     std::atomic<bool> Connected{true};
     const DeviceType Type{};
 
@@ -295,7 +290,7 @@ struct DeviceBase {
     std::atomic<uint> mMixCount{0u};
 
     // Contexts created on this device
-    std::atomic<al::FlexArray<ContextBase*>*> mContexts{nullptr};
+    al::atomic_unique_ptr<al::FlexArray<ContextBase*>> mContexts;
 
 
     DeviceBase(DeviceType type);